Added back helper file accidentally deleted during test block 219 migration.

tests/lib/mirrors/deferred_mirrors_metatarget_test.dart

Index: tests/lib/mirrors/deferred_mirrors_metatarget_test.dart
diff --git a/tests/lib/mirrors/deferred_mirrors_metatarget_test.dart b/tests/lib/mirrors/deferred_mirrors_metatarget_test.dart
deleted file mode 100644
index f0091c8f328d38d2d0b016f9512670f0f6253dcf..0000000000000000000000000000000000000000
--- a/tests/lib/mirrors/deferred_mirrors_metatarget_test.dart
+++ /dev/null
@@ -1,18 +0,0 @@
-// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-/// Test that metaTargets can be reached via the mirrorSystem.
-
-import 'package:async_helper/async_helper.dart';
-import 'package:expect/expect.dart';
-
-import "deferred_mirrors_metatarget_lib.dart" deferred as lib;
-
-void main() {
-  asyncStart();
-  lib.loadLibrary().then((_) {
-    Expect.equals("A", lib.foo());
-    asyncEnd();
-  });
-}